ftp://ftp.mrunix.net/pub/webalizer/README
has all the info you need:
an excerpt:
-r name This option allows hiding of referrers from the "Top Referrer"
table in the report. Referrers are URL's, either on your own
local site or a remote site, that referred the user to a URL
on your web server. This option is normally used to hide
your own server from the table, as your own pages are usually
the top referrers to your own pages (well, you get the idea).
You must have a web server that includes referrer information
in the log files for this option to be of any use.
don't forget, if you have one webalizer.conf file,
then this will apply to all domain's stats
